On June 12, University of Illinois Police traced the car to Christensen, a former graduate student earned a masters degree in physics in May, according to a university spokeswoman and the criminal complaint filed by the FBI.

Christensen initially said he couldn't recall his whereabouts on June 9, later telling police that "he must have been either sleeping or he was playing video games at his residence all day," according to the complaint.

"Based on this, and other facts uncovered during the investigation of this matter, law enforcement agents believe that Ms. Zhang is no longer alive," the complaint concludes.

Christensen will remain in law enforcement custody pending his initial federal court appearance in Urbana scheduled on Monday, July 3, at 10 a.m., authorities said. Attorney information for the accused was not immediately available.

A prayer vigil planned for Saturday was canceled in the wake of the alleged kidnapper's arrest and news of Zhang’s possible death.

"We hope they are wrong, but trust they have creditable information to make this statement," organizers Kim Tee and Randy Tom said in a joint statement late Friday night. "Please keep Ying Ying's family in your thought and prayers, and may God watch over them."